Electrolyzer Sizing and Techno‐Economic Assessment of Small‐Hydropower‐Based Green Hydrogen Using 3 Years of Hourly Generation Data

Small hydropower can provide a comparatively persistent renewable‐electricity profile for water electrolysis, but electrolyzer sizing requires a compromise between renewable‐energy capture and equipment utilization. This study evaluates a planned green‐hydrogen system at Miryang Dam, Republic of Korea, using 26,280 h of measured generation data from two 650 kW units during 2021–2023. A 1 MW PEM electrolyzer was simulated by hourly load following, and capacities from 300 to 1200 kW were screened using an equal‐weight ideal‐point criterion and marginal hydrogen‐production gain. The planned 1 MW configuration captured 98.11% of available hydropower energy, achieved a 59.93% capacity factor, and produced 93.75 t‐H 2 /year. The criterion identified 600 kW as the technically balanced capacity, with 84.71% capture, 86.25% capacity factor, and 80.95 t‐H 2 /year. Incremental hydrogen gain declined from 7.03 t/year for the 500–600 kW increase to 3.82 t/year for 600–700 kW. At a PPA price of KRW 160/kWh, audited operating and full LCOH were KRW 20,137/kg‐H 2 and 27,209/kg‐H 2 . The results show that sizing based solely on peak hydropower output can overestimate the electrolyzer capacity required for efficient system utilization.